There are many reasons for back pain, which is estimated to occur in about 80% of the population at some point in their lifetime. The pain may originate from a number of different reasons or causes including, but not limited to, ligamentous/muscular injury to the paravertebral soft tissues, facet joint(s), disc internal derangement, compression of spinal nerves and instability of the spinal column. Conservative treatment usually helps ameliorate the discomfort. Life style modifications, rest, heat, cold therapy, anti-inflammatory medications, physical therapy, losing weight, conditioning the spinal musculature and abdominal muscles, therapeutic cortisone injections, etc. may help decrease the back discomfort. In some cases, however, back pain persists despite conservative treatment.
When conservative treatment fails to sufficiently reduce the patient's pain and improve the patient's quality of life, surgical correction of the spinal column may be performed. There are several types of procedures that may be performed in an attempt to alleviate back pain. For example, spinal decompression can be performed to relieve compression from spinal nerves that are being impinged by a protruding disc or boney/soft tissue overgrowth (lamina, facet, ligamentum flavum) into the spinal canal.
Another procedure is a fusion or arthrodesis of the spinal column. A fusion is sometimes utilized to stop the painful motion of the mobile section of the spinal column. Examples of where fusion may be utilized include where there is instability of the spinal segment (a disc and its adjoining vertebrae), pain from a degenerated and torn disc, or arthritic condition of the facet joint which may lead to pain.
A fusion is performed by preparing the boney surfaces of the adjoining vertebrae. Typically, the soft tissues (disc, cartilaginous intervertebral endplates, facet joint cartilage/capsule, and/or musculature from the transverse process/par articularis) are removed to expose the intended fusion area boney surfaces. Then, bone graft or other bone growth promoting substances are placed in the area of the intended fusion area (intervertebral disc space, interspinous process space, lateral gutter between the transverse process and/or in the facet joints).
Instrumentation of the spinal segment that is being fused is commonly performed to help immobilize that segment until a solid fusion occurs. Cages, screws, rods, plates and/or the like are used to immobilize the spinal segment until a solid fusion occurs.
Common instrumentation techniques include an interbody fusion with screws, cage(s) or plate fixation (PLIF—posterior lumbar interbody fusion; ALIF—anterior lumbar interbody fusion; XLIF extreme lateral interbody fusion), posterior pedicle instrumentation, transfacet pedicle screw fixation, interspinous process spacer, translaminar facet screw fixation and a combination of one of the above mentioned instrumentations. Each one of these spinal instrumentations has unique risks associated with their use. An ALIF has a potential risk of injuring an abdominal organ or a major vascular vessel, and/or causing retrograde ejaculation in males. An XLIF may injure a nerve root, lumbar plexus or sympathetic chain, major vascular vessels and/or abdominal organs. A PLIF has the risk of an epidural scar, nerve root injury, and/or dural tear. Posterior instrumentation usually entails inserting pedicle screws and connecting them to a rod or plate. Placement of the pedicle screws can be difficult and incorrect screw placement can cause nerve injury, an epidural tear or a vascular injury. Further, pedicle or facet screw placement usually requires large, invasive exposure to properly place the screws. Even minimally invasive exposure techniques require two moderately sized incisions in order to place the hardware.
Over 350,000 spinal fusions are currently done in the US yearly to alleviate spinal pain. With the increased age of the population, it is anticipated that complaints of degenerative problems of the spine will increase. Hence, spinal fusions and the need to stabilize the spine will become even more prevalent.
Two known products that are in the market for lumbar facet fusion are the TruFUSE allograft and a transfacet screw type of fixation. The TruFUSE allograft is a facet fusion allograft with a Mores taper that is placed into the facet joint. Allograft and/or autograft are typically placed into the facet joint to help induce a fusion across the joint.
There are many types of screws that have been used to perform a transfacet fixation. The technique in which it has been performed varies. A translaminar facet screw fixation, transfacet pedicle screw fixation and a pedicle screw fixation have been used to immobilize the facet joint. A Facet Fixation System has also been introduced by US SPINE to achieve a transfacet fixation.
The present invention is unique from these and all other spinal fusion devices in that it is based on an encircling device and/or top cap to immobilize the facet joint and which allows fusion of the facet joint. This invention would stabilize the facets in a matter that pedicle screws in two vertebral bodies would not be necessary. This fusion device and technique could be performed in a minimally invasive manner and potentially be performed as an outpatient procedure.